A court in Baghdad issued arrest warrants in February 2006, and two years later the Iraqi interior minister, Jawad al Boulani, vowed to do his best to track down the killers after receiving a letter from three of the dead men's families. But there seemed to have been little progress until February this year, when eight Iraqis were arrested over the killings.

Charges against one of the eight Iraqis were dropped earlier this year, which leaves two men now facing court. "The judge indicated that, pending confirmation of the identity of one of the remaining two suspects in custody, both will face trial," Harvey said.

An MoD spokesman said: "The UK government is committed to seeing the killers brought to justice."

None of the families contacted by the Guardian wished to comment.

But, speaking after the arrests earlier this year, Russell Aston's father, Mike, said he was "absolutely" happy that the men were facing trial.

Mike Aston, who has campaigned for an independent investigation into the Red Caps' deaths, said that the MoD had been "stuck between a rock and a hard place" over the arrests because of sensitivities over British involvement in the case. Aston also said that he doubted the arrests would have happened if it was not for the efforts of the families.

"It's been a long time coming and it's only because of pressure from Reg Keys [father of L/Cpl Keys] and myself that these arrests have been made," he said. "We've had six-and-a-half years of pushing for this. If it wasn't for three of the fathers the six RMP would've been forgotten."

The Oxfordshire coroner Nicholas Gardiner, who conducted the three-week inquest into the Red Caps' deaths, ruled that the men had been killed unlawfully.

The inquest heard of a shortage of iridium satellite phones and limitations on radio communication leading to patrols being sent out "blind". The shortage led to direct breaches of commands requiring units leaving the base to carry a telephone.

Gardiner said he would write to the then defence secretary, John Reid, with a series of recommendations about radio equipment and command procedures "to prevent the recurrence of fatalities".